Modeling the Seismic Response of Heavy Oil Sands to Heat and Steam, Coalinga Field
WALLS, JOEL, Rock Solid Images, Morgan Hill, CA; MAGGIE SMITH, Rock Solid Images, Houston, TX; WILLIAM KEMPNER, Chevron USA Production Co, Bakersfield, CA
Well log data from three wells were used to model the seismic response of heavy oil sands in the Temblor formation, Coalinga Field, California. The purpose of the modeling study was to establish the feasibility of a possible seismic reservoir characterization project.
Two of the wells had multi-depth resistivity logs. The resistivity curves for four depths of investigation ranging from 10 to 90 inches were examined. Over the intervals in question, there was only about 5% difference in Sw, therefore, no corrections for mud invasion were necessary.
A dipole shear wave log was available for one well. Two models for Vs prediction were tested, Greenberg-Castagna and Unconsolidated Sand. In the Temblor sands, the Greenberg-Castagna method provided a closer estimate than the Unconsolidated Sand model so this tool was used to compute Vs for the wells which had no dipole sonic log.
The fluid types that were modeled in the reservoir zones were "hot oil" and "steam". Fluid substitution was only performed in reservoir zones comprising the Temblor sands and only where total porosity was greater than 30% and Vclay was less than 40%. The average magnitude of the Vp and Vs resulting from the fluid substitution calculations on well log data showed good agreement with laboratory core results. It was also determined that the seismic data should be sufficiently sensitive to the fluid properties to make the seismic reservoir characterization work feasible. The initial results of the characterization are useful in defining the lateral distribution of sands within a complex depositional system although the actual properties of the sands need further refinement.
AAPG Search and Discovery Article #90911©2000 AAPG Pacific Section and Western Region Society of Petroleum Engineers, Long Beach, California